﻿//
// Copyright (c) 2011 Canyala Innovation AB
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and 
// associated documentation files (the "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
// copies of the Software, and to permit persons to whom the Software is furnished to do so, 
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT 
// NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH 
// THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 
//

using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Linq;
using System.Text;

namespace Canyala.Lagoon.Functional
{
    /// <summary>
    /// Static class to be used to generate a IComparer with custom behaviour
    /// for LINQ expressions.
    /// </summary>
    /// <remarks>
    /// Using the Comparison class you can simplify the situation where you need to supply 
    /// an IComparer with a Linq expression.
    /// 
    /// var products = GetProducts().OrderBy(x => x.ProductId,  Comparison.With((x,y) => String.Compare(x.Name, y.Name)));
    /// </remarks>
    public static class Comparison 
    {
        /// <summary>
        /// Returns a generic instance of the IComparer interface where
        /// the Compare() method calls the function given.
        /// </summary>
        /// <typeparam name="T">Type of objects to compare</typeparam>
        /// <param name="func">The compare function to use.</param>
        /// <returns>New instance of the GenericComparer class using the function given.</returns>
        public static IComparer<T> With<T>(Func<T, T, int> func)
        {
            #region Requires
            Contract.Requires<ArgumentNullException>(func != null, "func");
            #endregion
            #region Ensures
            Contract.Ensures(Contract.Result<IComparer<T>>() != null);
            #endregion

            return new GenericComparer<T>(func);
        }
    }
}
